Three weeks ago more than 300 schoolgirls were kidnapped by Islamic extremists in Chibok, Nigeria, a town in the northeastern part of the country --- and 276 girls are still missing.

The girls were taken in the dark of night from their dormitory when armed men burst into the Chibok Government Girls Secondary School. That was on April 15. This week, the Islamic militant group Boko Haram claimed responsibility for the kidnappings.

What they knew was chilling: The men were not government soldiers at all. They were members of the ruthless Islamic extremist group called Boko Haram. They kidnapped the entire group of girls and drove them away in pickup trucks into the dense forest.

Fifty three students escaped that day. According to AP, of the girls still missing, about 20 are ill and at least two have died of snakebites.

The AP also reports that a local government official received a warning call about the armed militants at 11 p.m. on April 14.

[Official Bana Lawal] alerted the 15 soldiers guarding Chibok, he said. Then he roused sleeping residents and told them to flee into the bush and the nearby hills. The soldiers sent an SOS to the nearest barracks, about 30 miles (48 kilometers) away, an hour's drive on a dirt road.

No help arrived.

The militants showed up hours later and the soldiers fought them, but they were outnumbered and outgunned, and later fled for their lives. The extremists then headed for the boarding school.

Who is Boko Haram?

Boko Haram is an Islamic extremist group in northern Nigeria, a region of the country that is predominately Muslim. Southern Nigeria is largely Christian. According to the BBC, the group is fighting to create an Islamic state and believes it is forbidden for Muslims to take part in activities associated with Western society.

Boko originally means fake but came to signify Western education, while haram means forbidden.

The group has perpetrated various attacks and bombings in Nigeria. In 2013, the State Department designated the group a terrorist organization.

According to Amnesty International, Boko Haram was responsible for the deaths of 1,500 people in the first three months of 2014 and more than half of the victims were civilians. USA Today reported that the group was responsible for 3,982 deaths so far this year.

The US government has a $7 million bounty for Abubakar Shekau, the leader of Boko Haram, which is $2 million more than the bounty for the Afghan Taliban’s top man, Time reported.

There have been reports of the girls being trafficked and sold into slavery.

On Monday, the leader of Boko Haram claimed responsibility for the kidnapping and threatened to sell the girls. In a video, Abubakar Shekau says, “I abducted your girls” and ‘‘By Allah, I will sell them in the marketplace.’’

Last week, there were reports that the girls trafficked and forced to “marry” their captors, but it’s unclear if the video was made before or after those reports, the AP reports.

In the video, Shekau also said the students "will remain slaves with us." That appears a reference to the ancient jihadi custom of enslaving women captured in a holy war, who then can be used for sex.

"They are slaves and I will sell them because I have the market to sell them," he said, speaking in the Hausa language of northern Nigeria.

The group also threatened to abduct more girls and attack more schools. Today, there are reports that the extremists have kidnapped eight more girls, USA Today reports.

Boko Haram has targeted schools in the past, but this is the first large-scale targeting of girls, NPR reports.

"In the past, when boys have been killed at schools that have been raided, the girls have been spared, told to go home, get married and give up Western education," [NPR Africa correspondent Ofeibea Quist-Arcton] says.

Where are the missing schoolgirls?

Authorities do not know where the girls are. Locals in Chibok have formed search parties to look in the nearby Sambisa Forest, which is more than 23,000 square miles, as the military says it is diligently looking for the girls, the AP reports.

Have any of the girls been rescued?

In this Monday April 21, 2014 file photo, four female students girls who escaped their Islamic extremist kidnappers.

Haruna Umar/ AP file photo

There have been no reports of the girls being rescued. The only girls that have been reunited with their families are the ones that escaped the night of the abduction.

What is the Nigerian government doing?

There had been little said by President Goodluck Jonathan until Sunday, when he made a public statement and said his administration was doing everything possible to find the girls. Jonathan said “everything must be done” to free the girls, the AP reports.

Jonathan said he has been asking for and getting help from the United States but that President Barack Obama has expressed concern to him about allegations of gross human rights abuses by security forces accused of summary executions and the killings in detention of thousands of people.

"I said, 'Send someone to see what we are doing and assist us, give us equipment that will help us, because we need sophisticated (equipment), don't just say there is some matter of alleged abuses,'" Jonathan said, describing one of two conversations with the U.S. leader.

Jonathan has created a committee to work with the local community on a strategy to free the girls.

Meanwhile there has been national outrage in Nigeria as the military has failed to rescue the girls. There has also been demonstrations in major cities in Nigeria over what protestors see as the government’s slow response and insensitivity to the girls’ plight, according the AP.

A leader of a protest march on Monday said Nigeria’s First Lady ordered two protesters arrested and expressed doubt there was any kidnapping, the AP reported.

What else is being done about the kidnappings?

International outcry is building as pressure on Nigeria mounts. In Nigeria, demonstrators have demanded action. In Washington , D.C.New York City, London, and other major cities, rallies have been held calling for the return of the girls. The outcry has also put pressure on the international community to step in.

The White House said that it is helping in the search for the missing girls and is sending a team of military and law enforcement personnel to provide intelligence expertise and hostage negotiating assistance to Nigerian investigators. According to ABC News, the FBI is also ready for a possible deployment to help with the situation.

Britain has also offered to help in the rescue of the kidnapped girls. According to The Globe and Mail, British Foreign Minister William Hague offered assistance in securing the girls’ release.